3908 Nyx is an Amor and Mars-crosser asteroid. It was discovered by Hans-Emil Schuster on August 6, 1980, and is named after Nyx, the Greek goddess of the night, after which Pluto's moon Nix is also named.

In Greek mythology, Nyx (???, "night", Nox in Roman translation) was the primordial goddess of the night. A shadowy figure, Nyx stood at or near the beginning of creation, and was the mother of personified gods such as Hypnos (sleep) and Thanatos (death).